Fluidized Bed Gasifier Bottom Ash Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current gasification processes, such as the high-temperature Winkler process, face challenges in efficiently managing carbonaceous ash streams produced during the conversion of fuels like coal and biomass, requiring additional facilities for post-treatment and leading to reduced synthesis gas yield due to oxygen addition in the post-gasification zone.
Innovation Solution
A plant with a gasification reactor featuring a fluidized bed zone and an additional fluidized bed combustion chamber below it, where the carbon-containing ash stream is oxidized using an oxidizing agent, including oxygen, air, and steam, allowing for effective combustion and fluidization without additional fluid requirements, and optimizing oxygen content based on measured temperature and carbon content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If oxygen is added to the post-gasification zone to increase temperature and accelerate gasification reactions, then the gasification reaction rate is improved, but the synthesis gas yield is reduced due to partial combustion of CO and H2
Solution Approach 1:
The gasification system is divided into two separate zones: a fluidized bed gasification zone for converting fuel to synthesis gas, and a separate combustion chamber for oxidizing bottom ash. This segmentation prevents oxygen from contacting synthesis gas, avoiding combustion losses while maintaining high reaction rates in each zone independently.
Solution Approach 2:
The bottom ash acts as an intermediary carrier of carbon from the gasification zone to the combustion chamber. By oxidizing carbon in the bottom ash in a separate combustion zone rather than adding oxygen directly to the gasification zone, the system achieves carbon removal without compromising synthesis gas yield.
2Use of energy by moving object
If external furnaces are used for post-treatment of carbonaceous bottom product to utilize energy and prepare for landfill, then energy utilization is improved, but additional facilities and operational complexity are required
Solution Approach 1:
The bottom ash oxidation process is merged with the existing gasification system by using the combustion chamber as an integrated component. The combustion chamber serves dual purposes: oxidizing bottom ash to remove carbon and generating heat that can be utilized within the same system, eliminating the need for separate external furnaces.
Solution Approach 2:
The gasification system performs its own bottom ash treatment through the integrated combustion chamber. The system oxidizes its own bottom product in-house, converting carbonaceous waste into useful heat while simplifying the overall process configuration and eliminating external treatment facilities.
3Stability of the object's composition
If the fluidized bed temperature is kept below the ash softening point to avoid particle agglomerations, then operational stability is improved, but the temperature is insufficient for complete carbon oxidation in bottom product
Solution Approach 1:
The system segments the thermal processes into two distinct temperature zones: the fluidized bed gasification zone operates below the ash softening point to maintain stability, while the separate combustion chamber operates at higher temperatures to achieve complete carbon oxidation in the bottom ash.
Solution Approach 2:
The bottom ash serves as an intermediary that transports carbon from the low-temperature gasification zone to the high-temperature combustion chamber, enabling carbon oxidation at temperatures that would be too high for the gasification zone while maintaining fluidized bed stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables economical and safe gasification at high pressures, reducing the need for external post-treatment of ash streams and enhancing synthesis gas yield by optimizing combustion conditions within the fluidized bed combustion chamber.
Implementation Method 1
the bottom product is oxidized by supplying an oxidizing agent
Implementation Method 2
the carbon-containing ash stream is oxidized using an oxidizing agent, including oxygen, air, and steam, allowing for effective combustion
Implementation Method 3
the supply device (27, 28) is designed in such a way that the oxygen and/or air and/or or steam and/or CO 2 -containing fluid flow, the bottom product to be burned in the additional fluidized bed combustion chamber (12) is fluidized
Implementation Method 4
the recirculated raw gas is compressed by means of at least one compressor before it is introduced into the additional fluidized-bed combustion chamber
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a system for converting carbon-containing fuels into synthesis gas, comprising a gasification reactor (10), which has at least one fluidized-bed zone (11), in which the fuels are gasified by means of suitable gasification agents, wherein a carbon-containing ash flow is produced as a bottom product in a bottom region arranged below the fluidized-bed zone (11) and wherein a device is arranged below the gasification reactor (10), in which device the bottom product is oxidized by the feeding of an oxidant, wherein an additional fluidized-bed combustion chamber (12) is arranged below the fluidized-bed zone (11) of the gasification reactor (10) as a device for oxidizing the bottom product.